1. Field of the Invention
The present invention relates to optical switches, and more particularly, to mechanically actuated optical switches.
2. Background
Optical switches have been developed for switching optical networks in broadband telecommunications systems. Because of increasing demand for high speed broadband data communications, optical wavebands including infrared and visible light wavelengths are increasingly being used as data carriers in telecommunications systems to satisfy the demand for high speed broadband data transmission. Conventional optical switches have been implemented in a typical optical fiber telecommunications network to switch the optical paths of information-carrying light to different optical fiber cables.
Conventional optical switches typically fall into two broad categories of non-integrated optical switches and integrated optical switches. Among the non-integrated optical switches, moving fibers have been used to change optical paths between different input or output fibers. In a conventional moving fiber switch, either the input optical fibers or the output optical fibers are moved mechanically to switch the optical path between different input or output optical fibers.
However, conventional moving fiber switches typically suffer from alignment problems because it is difficult to align the input and output fibers with a high degree of accuracy and repeatability. Alignment of single mode fibers can be especially difficult because of their small diameters. Even a slight misalignment between the selected input and output fibers through which optical transmission supposedly occurs may result in an unacceptably high insertion loss because the output fiber is not in the perfect position on the optical path to receive the light transmitted from the input fiber.
In order to avoid the problem of misalignment in a typical fiber moving switch, expensive and complicated mechanisms are usually required to move either the input or the output optical fibers to achieve acceptable alignment accuracy and repeatability. Furthermore, conventional moving fiber switches typically have slow switching speeds which may limit their applications. in optical fiber communications networks which require high-speed switching operations.
Moving reflectors have also been used in conventional non-integrated optical switches to switch optical paths between different input or output optical fibers instead of moving the input or output fibers for optical alignment. Moving reflector switches are usually capable of faster switching operations than conventional moving fiber switches. However, conventional reflector switches typically also suffer from the problems of mechanical stability and repeatability. After a large number of repeated on and off switching operations, the optical reflectors in a conventional reflector switch may deviate from their designed reflection angles because of the problems with mechanical stability and repeatability. Even a slight deviation of reflection angle may cause the optical path of reflected light to be misaligned with a respective output fiber or another reflector which is supposedly positioned to receive the reflected light.
Therefore, there is a need for an optical switch with a high degree of reliability after a large number of repeated on and off switching operations which are typically required in modern optical fiber telecommunications networks. Furthermore, there is a need for an optical switch which provides accurate optical alignments between the reflectors and the optical fibers without requiring expensive or delicate mechanical assemblies for switching the reflectors between their on and of f positions. Furthermore, there is a need for an optical switch which is capable of high speed switching operations for a plurality of input and output optical fibers simultaneously.
The present invention provides a mechanically actuated Mxc3x97N optical switch matrix, roughly comprising a plurality of primary optical ports, a plurality of secondary optical ports, a support plate having first and second surfaces opposite each other, a reflector array comprising a plurality of movable optical reflectors each capable of occupying an on position to reflect light from a respective one of the primary optical ports to a respective one of the secondary optical ports, and a plurality of actuators connected to the movable optical reflectors respectively to drive the movable optical reflectors between their on and off positions.
In an embodiment, the on positions of the movable optical reflectors are above the first surface of the support plate whereas the actuators are positioned below the second surface of the support plate. In a further embodiment, the support plate is provided with apertures, and the actuators are connected to the movable optical reflectors respectively through a plurality of levers which are movably positioned through the apertures in the support plate to drive the respective movable optical reflectors.
In an embodiment, each of the movable optical reflectors is capable of being switched to its on position when it is moved by the respective lever away from the first surface of the support plate to a predetermined position above the first surface of the support plate to intercept light on an incident optical path from the respective primary optical port. The movable optical reflector has a reflection surface angled with respect to the respective incident optical path when the movable optical reflector is in its on position to reflect the light onto a reflected optical path which leads to one of the output optical fibers. When the movable optical reflector is switched from its on position to its off position, it is moved by the lever away from the incident optical path toward the first surface of the support plate. In a further embodiment, the off position of the movable optical reflector is within the aperture in the support plate.
In an embodiment, the actuators comprise relay switches capable of generating repetitive movements in opposite directions. Either prisms or mirrors may be used as optical reflectors in the Mxc3x97N optical switch according to the present invention, although other types of optical reflectors may also be used. In an embodiment, the reflection surface of each of the optical reflectors is angled at 45xc2x0 with respect to its incident optical path to reflect the light onto a reflected optical path which is perpendicular to the matrix incident optical path.
In an embodiment, a plurality of lenses are provided adjacent terminations of the input and output optical fibers to collimate light on the respective optical paths. In a further embodiment, the lenses and end portions of the respective optical fibers adjacent their terminations are housed in a plurality of collimator assemblies, respectively, which are fixedly connected to the first surface of the support plate. In yet a further embodiment, the collimator assemblies are connected to the first surface of the support plate by laser welding for improved mechanical stability and reliability.
Advantageously, the mechanically actuated Mxc3x97N optical switch matrix according to the present invention can be implemented in an optical fiber telecommunications network which requires fast switching of optical communications signal channels between a plurality of input optical fibers and a plurality of output optical fibers. The Mxc3x97N optical switch matrix according to the present invention is able to achieve a high degree of mechanical reliability and repeatability for accurate optical alignments after a large number of frequent switching operations. Furthermore, optical switching can be achieved with a high degree of reliability without requiring expensive or delicate mechanisms for actuating the movable optical reflectors in the optical switch matrix according to the present invention.